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Thread: Seagate ST4096 Hard Drive Repair

  1. #1

    Default Seagate ST4096 Hard Drive Repair

    Hi,
    I recently bought an IBM 5170 that I am trying to fix and it came with a Seagate ST4096 80MB MFM hard drive that is not working. When I tried to power the drive on, I heard a pop and the drive released a bit of magic smoke. When I looked on the board on the bottom of the drive, I noticed that there was a burn mark on the board and that there was a missing surface mount component right in the middle of the burn mark. I have attached a picture of the board that I found online and I have circled the missing component in the image. Can someone tell me the type and value of the part so that I can replace it and hopefully get this drive working again? I have looked for schematics online, but I can't find any, so I am hoping that someone will have a working drive that they can check the component on.

    Thanks!
    Alex
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  2. #2

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    Problem is, that's an unmarked cap...so you'd almost have to find an identical drive to pull one from (and that wouldn't necessarily be the exact value since revisions of boards may change the value). Bigger issue is finding out what caused it to blow first, before you change it out. That type of cap isn't like an electrolytic nor does it have a high failure-rate.

    Finally, a drive that old may have tons of problems besides the capacitor issue.

  3. #3

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    I'm thinking it is a zero ohm resistor and it popped because of the 22uf tantalum in the corner. You might check that the tantalum is not shorted.
    It might be a capacitor as well so wait tell others reply.
    Dwight

  4. #4

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    Quote Originally Posted by T-R-A View Post
    Problem is, that's an unmarked cap...so you'd almost have to find an identical drive to pull one from (and that wouldn't necessarily be the exact value since revisions of boards may change the value). Bigger issue is finding out what caused it to blow first, before you change it out. That type of cap isn't like an electrolytic nor does it have a high failure-rate.

    Finally, a drive that old may have tons of problems besides the capacitor issue.
    It may be a ceramic capacitor but these rarely fail. I agree it looks like one. I think it would be wise to check with someone that has a ST4096. These were common drives.
    Dwight

  5. #5
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    I found a half-decent image of the ST4096 circuit board ... maybe this will help as some of the component values are visible.

    https://amaus.net/static/S100/seagat...lectronics.jpg

  6. #6

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    Quote Originally Posted by T-R-A View Post
    Finally, a drive that old may have tons of problems besides the capacitor issue.
    Ditto... IOW, it may be a rabbit hole.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  7. #7
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    OR it might not have any problems at all. I have a lot of old Seagate drives and many of them are still working well. Why would this drive be any different? IF they spin and don't sound too crunchy, usually a low level format will bring it to life.

  8. #8
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    Quote Originally Posted by Dwight Elvey View Post
    I'm thinking it is a zero ohm resistor and it popped because of the 22uf tantalum in the corner. You might check that the tantalum is not shorted.
    It might be a capacitor as well so wait tell others reply.
    Dwight
    I think you're right; it measures 0.3 Ohms on a drive in front of me. Definitely check that tantalum!

  9. #9

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    Quote Originally Posted by chris_nh View Post
    OR it might not have any problems at all. I have a lot of old Seagate drives and many of them are still working well. Why would this drive be any different? IF they spin and don't sound too crunchy, usually a low level format will bring it to life.
    That's if you can LLF it. I have a stack of MFM and RLL drives that spin and run quietly that can't be LLFed. I think they have track zero issues which is a not too uncommon ailment for drives of that period.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  10. #10
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    Either track 0 or I found a cracked ribbon cable (heads) the other day on a ST235R drive which runs quiet and was previously working, but now the drive is unreadable because of the broken ribbon. I think even that might still be fixable someday , but yeah, Track 0 is sometimes not.

    I've also found that some drives will fail SSTOR's automatic LLF, but will work with a bounded init of default cylinders instead. I just revived an ST412 with that condition by performing a bounded init, where it previously would not LLF.

    --CB

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